UK Spur off a 4mm twin and earth, 32amp radial

[JLH520]

I have a dedicated radial from the consumer unit to my conservatory. This was installed using 4mm twin and earth as it gives the option to use multiple electric heaters on a 32amp breaker if needed. The circuit consists 4 double sockets plus one single socket on the end, in a weatherproofed box on the wall outside. As it happens, I rarely need to use electric heaters in there, as there are plumbed radiators too, so the radial is easily over specced and currently has only a 16amp breaker.

Now I need to add two extra double sockets outside to power two 2500 watt infra red heaters under a gazebo (each has a 13 amp 3 pin UK plug fitted, they won’t be hardwired). I am hoping to be able to add these sockets by running a spur from the conservatory radial circuit as it could comfortably cope with the draw from the heaters. My intention was to continue a 4mm twin and earth spur to these additional two sockets outside so that the whole radial is safely capable of handling 32 amps.

The problem is that a fused connection unit which handles a fuse above 13 amp doesn’t seem to exist, so I’m wondering how best to safely connect this spur to my radial circuit and isolate the outside circuits if need be?

Any helpful suggestions on how to implement this would be greatly appreciated

 

[buzzlightyear]

Any helpful suggestions on how to implement this would be greatly appreciated

A spark will advice is in order.

 

[ImpededLoop]

A 45A double pole switch would be suitable if you want a means of isolating the external part of the circuit.

 

[JLH520]

A 45A double pole switch would be suitable if you want a means of isolating the external part of the circuit.

Ok, thanks for the suggestion. I am aware that typically, taking a spur off a radial when there is more than one additional socket to be added, a 13 amp fused connection unit should be used - then you can add as many sockets as you like on that spur (within reason, and please correct me if I am wrong here!).
I suspected this would be the same when using 4mm T&E (on both the original radial and the new spur), capable of carrying more amps, only this would need a higher rated fuse (up to 32amps?)
Is it acceptable within the regs to add just a double pole switch at the end of the indoor section of the radial so that I can isolate all the outside sockets beyond it? Not sure if regs also require some sort of additional fused unit before going outside with a further 3 sockets (1 existing, plus 2 new additional sockets).
Thanks.

 

[telectrix]

Ok, thanks for the suggestion. I am aware that typically, taking a spur off a radial when there is more than one additional socket to be added, a 13 amp fused connection unit should be used - then you can add as many sockets as you like on that spur (within reason, and please correct me if I am wrong here!).
I suspected this would be the same when using 4mm T&E (on both the original radial and the new spur), capable of carrying more amps, only this would need a higher rated fuse (up to 32amps?)
Is it acceptable within the regs to add just a double pole switch at the end of the indoor section of the radial so that I can isolate all the outside sockets beyond it? Not sure if regs also require some sort of additional fused unit before going outside with a further 3 sockets (1 existing, plus 2 new additional sockets).
Thanks.

let me correct you first. no disrespect, but, 1. it's not pedantically a spur. a spur is only off a ring circuit. off a radial it's a branch.
2. as rthe MCB (up to 32A for a 4mm radial) will protect additional branches (in 4mm) from overload, a FCU is not required.

so just tap in where convenient. add a branch for the new sockets, uprate the MCB accordingl to the load )32A if clipped direct and not subject to derating due to insulation). happy days. ??

 

[AcDc50hz]

Ok, thanks for the suggestion. I am aware that typically, taking a spur off a radial when there is more than one additional socket to be added, a 13 amp fused connection unit should be used - then you can add as many sockets as you like on that spur (within reason, and please correct me if I am wrong here!).
I suspected this would be the same when using 4mm T&E (on both the original radial and the new spur), capable of carrying more amps, only this would need a higher rated fuse (up to 32amps?)
Is it acceptable within the regs to add just a double pole switch at the end of the indoor section of the radial so that I can isolate all the outside sockets beyond it? Not sure if regs also require some sort of additional fused unit before going outside with a further 3 sockets (1 existing, plus 2 new additional sockets).
Thanks.

Surely if your continuing the circuit from the last socket it wouldn't be classed as a spur youd just be extending the radial circuit?

 

[goasis]

Ok, thanks for the suggestion. I am aware that typically, taking a spur off a radial when there is more than one additional socket to be added, a 13 amp fused connection unit should be used - then you can add as many sockets as you like on that spur (within reason, and please correct me if I am wrong here!).
I suspected this would be the same when using 4mm T&E (on both the original radial and the new spur), capable of carrying more amps, only this would need a higher rated fuse (up to 32amps?)
Is it acceptable within the regs to add just a double pole switch at the end of the indoor section of the radial so that I can isolate all the outside sockets beyond it? Not sure if regs also require some sort of additional fused unit before going outside with a further 3 sockets (1 existing, plus 2 new additional sockets).
Thanks.

U can't spur off a radial... its just a case of extending the radial circuit. Would you consider it a 'spur'if you went from the last socket on the circuit? You're thinking of the rules for adding additional outlets from a ring final circuit arrangement.

 

[ImpededLoop]

What Telectrix said! ?

................ .................. ........... Five wordd

 

[Petej999]

I have a dedicated radial from the consumer unit to my conservatory. This was installed using 4mm twin and earth as it gives the option to use multiple electric heaters on a 32amp breaker if needed. The circuit consists 4 double sockets plus one single socket on the end, in a weatherproofed box on the wall outside. As it happens, I rarely need to use electric heaters in there, as there are plumbed radiators too, so the radial is easily over specced and currently has only a 16amp breaker.

Now I need to add two extra double sockets outside to power two 2500 watt infra red heaters under a gazebo (each has a 13 amp 3 pin UK plug fitted, they won’t be hardwired). I am hoping to be able to add these sockets by running a spur from the conservatory radial circuit as it could comfortably cope with the draw from the heaters. My intention was to continue a 4mm twin and earth spur to these additional two sockets outside so that the whole radial is safely capable of handling 32 amps.

The problem is that a fused connection unit which handles a fuse above 13 amp doesn’t seem to exist, so I’m wondering how best to safely connect this spur to my radial circuit and isolate the outside circuits if need be?

Any helpful suggestions on how to implement this would be greatly appreciated

IT is a

I have a dedicated radial from the consumer unit to my conservatory. This was installed using 4mm twin and earth as it gives the option to use multiple electric heaters on a 32amp breaker if needed. The circuit consists 4 double sockets plus one single socket on the end, in a weatherproofed box on the wall outside. As it happens, I rarely need to use electric heaters in there, as there are plumbed radiators too, so the radial is easily over specced and currently has only a 16amp breaker.

Now I need to add two extra double sockets outside to power two 2500 watt infra red heaters under a gazebo (each has a 13 amp 3 pin UK plug fitted, they won’t be hardwired). I am hoping to be able to add these sockets by running a spur from the conservatory radial circuit as it could comfortably cope with the draw from the heaters. My intention was to continue a 4mm twin and earth spur to these additional two sockets outside so that the whole radial is safely capable of handling 32 amps.

The problem is that a fused connection unit which handles a fuse above 13 amp doesn’t seem to exist, so I’m wondering how best to safely connect this spur to my radial circuit and isolate the outside circuits if need be?

Any helpful suggestions on how to implement this would be greatly appreciated

There is a recommendation that loads of 2Kw and above need to be on their own dedicated circuit, not fed via a 13 A spur

 

[telectrix]

never agreed with thatpete. it may have been relevant when a house had only 1 RFC (ncluding kitchen) but these days it's rare to see a non-kitchen RFC loaded to >5A or 6A. we had a 2.2kW hot tub , 2.2kW sauna, 3 freezers, washer, fumble dryer, all on a 16A radial (garage). cable used to get slightly warm. made ito a RFC (when sauna was added) to a 32A RFC just to be safe.

 

[littlespark]

There is a recommendation that loads of 2Kw and above need to be on their own dedicated circuit, not fed via a 13 A spur

I think we've established that this wont be on a 13A spur... its on a radial, wired in 4mm, which could have a 32A OCPD if someone changes it back from a 16.

As above, if you want to isolate the outside sockets, then a 45A double pole switch ... (for a cooker or shower - no fuse) before going outside will suffice.


Edit, Afterthought: If youre doing any work to this circuit, you must ensure it is RCD protected... i dont think it was mentioned on the OP

 

[westward10]

There is no reason why it cannot be extended in 4.0 and upgraded to 32A however as previously mentioned the installation method may not permit it. If you are going to contain this cable in conduit then 32A is not an option.

 

[JLH520]

Thank you all for (A) putting me straight on a couple of points, and (B) providing the answers I was looking for.

To clarify a couple of points - yes the circuit is, and will continue to be RCD protected and I will extend onto the end of the radial, rather than cutting in between the existing sockets (not sure if that would change anything.)

I will also change the circuit MCB to a 32 amp to cope with the heaters.

Thanks again.

 

[telectrix]

Thank you all for (A) putting me straight on a couple of points, and (B) providing the answers I was looking for.

To clarify a couple of points - yes the circuit is, and will continue to be RCD protected and I will extend onto the end of the radial, rather than cutting in between the existing sockets (not sure if that would change anything.)

I will also change the circuit MCB to a 32 amp to cope with the heaters.

Thanks again.

spot on.

 

[westward10]

Thank you all for (A) putting me straight on a couple of points, and (B) providing the answers I was looking for.

To clarify a couple of points - yes the circuit is, and will continue to be RCD protected and I will extend onto the end of the radial, rather than cutting in between the existing sockets (not sure if that would change anything.)

I will also change the circuit MCB to a 32 amp to cope with the heaters.

Thanks again.

How is the new cable going to be installed.

 

[JLH520]

How is the new cable going to be installed.

…was planning to run 4mm SWA to the new sockets. Had planned to use a short run (approx 1 metre) of 4mm twin and earth in a conduit between the two sockets rather than use SWA between the two sockets. Is 4mm T&E permissible in conduit over this short distance?

 

[westward10]

…was planning to run 4mm SWA to the new sockets. Had planned to use a short run (approx 1 metre) of 4mm twin and earth in a conduit between the two sockets rather than use SWA between the two sockets. Is 4mm T&E permissible in conduit over this short distance?

Contained in conduit it would not be rated at 32A unless it is singles.

 

[JLH520]

Contained in conduit it would not be rated at 32A unless it is singles.

Ok understood, thanks.

 

[brianmoooore]

If the bit in the conduit only feeds one socket, then it doesn't need overload protection - just short circuit protection.

 

[JLH520]

If the bit in the conduit only feeds one socket, then it doesn't need overload protection - just short circuit protection.

Ok, thanks Brian, that helps.